The problem with humans is that we are granted with terrible foresight. We have great hindsight. Every new adventure, looks like nirvana when looking ahead. We flooded with excitement to prospect of what and where we could be going. Through romance in there and we are hopeless. We become addicted to a fleeting feeling that can really never be quenched. Maybe in short bursts, but not over long periods. Like with the metaphor you used about working out, we can sustain for short bursts and ride the dopamine releases, but the outcomes are either to far out or completely out of bounds. There either has to be an unstoppable "want to" or a undeniable love for whatever it is to sustain us to the desired outcome.
The other problem with humans, is that the finish line is a forever moving target. Our lives are filled with "if only" and "when I" statements that make getting to a point of happiness a virtual impossibility. As crazy as it sound, we have to let go of things to gain control of them.
FYI, you are the first ballet dancer that I have ever had the pleasure of speaking with. I am very interested in how being involved in that world impacted or related to your world outside of dance. I am sure that, like with many specialized communities, like dance or sports, sometimes the inner workings are much different than the outside world. Almost like a bubble.
RE: Assigning Too Much Value To The Reward